Highly efficient organic light-emitting device using substrate or electrode having nanosized half-spherical convex and method for preparing the same

ABSTRACT

The present invention provides a transparent substance formed with a plurality of continuous half-spherical convexes having a diameter of 25˜1,000 nm on its first main surface; an organic light-emitting device comprising a substrate, a first electrode, an organic material layer(s) and a second electrode, sequentially, characterized by having a plurality of continuous half-spherical convexes having a diameter of 25˜1,000 nm on the underside of the substrate that does not contact the first electrode and/or the upside of the second electrode that does not contact the organic material layer; and a method for preparing same using a porous aluminum oxide layer forming process.

TECHNICAL FIELD

The present invention relates to an organic light-emitting device,particularly an organic light-emitting device having non-planarstructure, and a method for preparing the same. More particularly, thepresent invention relates to a transparent substance having continuousnano-sized half-spherical convexes, a highly efficient organiclight-emitting device using the same, and a method for preparing thesame.

BACKGROUND ART

Organic electroluminescence means converts electrical energy into lightenergy by using organic materials. Its principle is explained asfollows. When voltage is applied between an anode and a cathode whilealigning an organic material layer between the anode and the cathode,holes are injected into the organic material layer from the anode, andelectrons are injected into the organic material layer from the cathode.When the injected holes couple with the injected electrons, excitons maybe formed and such excitons fall to the ground state to generate light.Such generated light is emitted through an anode, a cathode or bothelectrodes. Generally, an organic light-emitting device may beclassified as a top emission type, bottom emission type and bilateralemission type according to the emitting direction of light.

Recently, research has been actively carried out for preparing displaysor illumination units by using such electroluminescent phenomenon. Inaddition, techniques for depositing organic material layers in the formof a single layer to multi-layers are being actively studied in order toachieve effective organic light-emitting devices. Most currentlyavailable organic light-emitting devices include electrode layers andorganic material layers deposited in the form of a planar structure. Anorganic light-emitting device having a planar multi-layer structurecomprising electrode layers, and organic material multi-layers includinga hole injection layer (103), a hole transport layer (104), alight-emitting layer (105), and an electron transport layer (106) asshown in FIG. 1, has been widely used.

The light generated from a light-emitting layer of the organiclight-emitting device in FIG. 1 may pass through two different paths.Namely, the light may be emitted out of the organic light-emittingdevice through a transparent anode layer and glass substrate or mayremain in the organic light-emitting device by being reflected entirelyfrom the glass substrate surface or the anode surface. At this time, theamount of the light emitted out of the organic light-emitting device isonly about ½n² among the light generated from the light-emitting layer(wherein, n is the refractive index of an organic material layer). Ifthe refractive index of the organic material layer is 1.7, less than 17%of the light generated from the device can be emitted out of the organiclight-emitting device.

To solve the above problem and emit a large amount of light out of theorganic light-emitting device, an organic light-emitting deviceincluding a non-planar layer, i.e., non-planar structure, has beensuggested. The organic light-emitting device having a non-planarstructure can be prepared through the following two methods.

According to a first method, a photonic crystal having a gravure patternis formed on a glass substrate through a photolithography process beforea transparent anode is deposited on the glass substrate (see U.S. Pat.No. 6,630,684 and Appl. Phys. Lett. 82, 3779 issued in 2003 by Y. Lee etal.), or a corrugated pattern is formed on the glass substrate by usingan interference of light (see WO 2000/70691 and Adv. Mater. 13, 123issued in 2001 by B. J. Matterson et al.), for improving light-emittingefficiency. In detail, the former deposits an anode layer on the glasssubstrate, after forming the photonic crystal on the glass substrate andflattening the surface thereon by using SiN_(x). The latter deposits anelectrode layer and an organic material layer on the glass substratewhile maintaining a corrugated pattern, after forming the corrugatedpattern of transparent polymer on the glass substrate by usingphotoresist materials and an interference of light.

According to a second method, after preparing an organic light-emittingdevice having a planar structure as shown in FIG. 1, a micro-sized lensstructure (see WO 2003/007663 and J. Appl. Phys. 91, 3324 issued in 2002by S. Moller et al.) or a millimeter-sized lens structure (see WO2001/33598) is attached to a surface of a glass substrate of the organiclight-emitting device, thereby improving the light-emitting efficiencyof the device.

The above two methods can improve the light-emitting efficiency of thelight-emitting device. However, the above two methods cause problemswhen they are applied to an available product.

The first method uses the photolithography process, so it may beimpossible to economically form the photonic crystal structure or thecorrugated structure over a large-sized area. That is, in order toprepare the light-emitting device using the photonic crystal structure,it is necessary to sequentially carry out a deposition process, aphotolithography process, and an etching process. At this time, thesubstrate must be processed at least two times under a vacuum state. Inaddition, in order to prepare the light-emitting device using thecorrugated structure, it is necessary to perform the photolithographyprocess by using an interference of light. However, the photolithographyprocess is not adaptable for forming a uniform corrugated structure overa substrate having an area more than a few cm².

The second method has limitations when it is applied to a displaybecause the lens structure has a size in the range of about a fewmicrometers to a few millimeters. In addition, the second method is notadaptable for a large-sized area due to preparation work thereof.According to the lens structure disclosed in WO 2003/007663, a minimumsurface size of the lens structure is defined as a few μm such that theminimum surface size of the lens structure must be larger than themaximum wavelength of visible ray emitted from the organiclight-emitting device. In addition, according to the lens structuredisclosed in WO 2001/33598, the size of the lens structure must belarger than the size of one unit of an organic light-emitting device.

DISCLOSURE OF THE INVENTION

The inventors of the present invention have found that when an aluminumsubstrate having continuous nano-sized half-spherical recesses formed bya porous aluminum oxide layer forming process was used as a mold,continuous nano-sized half-spherical convexes can be economically formedon a large-sized transparent substance. In addition, the inventors havefound that continuous nano-sized half-spherical convexes can be formedon an organic light-emitting device by using the transparent substanceprepared by such method, and thus the light generated in an organicmaterial layer of the organic light-emitting device can be maximallyemitted out of the device.

Accordingly, it is an object of the present invention to provide atransparent substance having continuous nano-sized half-sphericalconvexes on its first main surface, an organic light-emitting devicehaving continuous nano-sized half-spherical convexes prepared byadhering the above transparent substance to a substrate and/or anelectrode of the device, and methods for preparing them.

One aspect of the present invention provides a transparent substancewherein a plurality of continuous half-spherical convexes having adiameter of 25-1,000 nm are formed on a first main surface of thetransparent substance.

Another aspect of the present invention provides a transparentsubstance, wherein a plurality of continuous half-spherical convexeshaving a diameter of 25-1,000 nm are formed on a first main surface ofthe transparent substance, prepared by a method comprising the steps of:

-   -   a) dipping an aluminum substrate having at least one aluminum        surface in an acid solution, and applying an oxidation voltage        of 10-400 V to the aluminum substrate so as to form an aluminum        oxide layer on one surface of the aluminum substrate, in such a        manner that a plurality of continuous recesses are formed on the        aluminum oxide layer, and a plurality of continuous recesses        having a curvature in identical direction to that of the        recesses on the aluminum oxide layer are formed on an interface        between the aluminum oxide layer and the aluminum substrate;    -   b) removing the aluminum oxide layer from the aluminum substrate        formed with the aluminum oxide layer thereon, thereby forming a        plurality of continuous half-spherical recesses having a        diameter of 25-1,000 nm on one surface of the aluminum        substrate; and    -   c) forming a plurality of continuous half-spherical convexes,        having a diameter of 25-1,000 nm, on the first main surface of a        transparent substance by using the aluminum substrate formed        with a plurality of continuous half-spherical recesses as a        mold.

Another aspect of the present invention provides an organiclight-emitting device comprising a substrate, a first electrode, anorganic material layer(s) and a second electrode in the sequentiallylaminated form, wherein a plurality of continuous half-sphericalconvexes having a diameter of 25-1,000 nm are formed on the underside ofthe substrate that does not contact the first electrode, the upside ofthe second electrode that does not contact the organic material layer,or both of them.

Another aspect of the present invention provides a method for preparinga transparent substance, wherein a plurality of continuoushalf-spherical convexes having a diameter of 25-1,000 nm are formed on afirst main surface of the transparent substance, comprising the stepsof:

-   -   a) dipping an aluminum substrate having at least one aluminum        surface in an acid solution, and applying an oxidation voltage        of 10-400 V to the aluminum substrate so as to form an aluminum        oxide layer on one surface of the aluminum substrate, in such a        manner that a plurality of continuous recesses are formed on the        aluminum oxide layer, and a plurality of continuous recesses        having a curvature in identical direction to that of the        recesses on the aluminum oxide layer are formed on an interface        between the aluminum oxide layer and the aluminum substrate;    -   b) removing the aluminum oxide layer from the aluminum substrate        formed with the aluminum oxide layer thereon, thereby forming a        plurality of continuous half-spherical recesses having a        diameter of 25-1,000 nm on one surface of the aluminum        substrate; and    -   c) forming a plurality of continuous half-spherical convexes,        having a diameter of 25-1,000 nm, on the first main surface of a        transparent substance by using the aluminum substrate formed        with a plurality of continuous half-spherical recesses as a        mold.

Another aspect of the present invention provides a method for preparingan organic light-emitting device, comprising the steps of:

-   -   a) preparing an organic light-emitting device by forming a first        electrode, an organic material layer(s) and a second electrode        on a substrate;    -   b) adhering a transparent substance to the underside of the        substrate that does not contact the first electrode, the upside        of the second electrode that does not contact the organic        material layer, or both of them in the organic light-emitting        device;    -   c) before or after the b) step, forming a plurality of        continuous half-spherical convexes, having a diameter of        25-1,000 nm, on the first main surface of the transparent        substance by a method comprising the steps of:        -   i) dipping an aluminum substrate having at least one            aluminum surface in an acid solution, and applying an            oxidation voltage of 10-400 V to the aluminum substrate so            as to form an aluminum oxide layer on one surface of the            aluminum substrate, in such a manner that a plurality of            continuous recesses are formed on the aluminum oxide layer,            and a plurality of continuous recesses having a curvature in            identical direction to that of the recesses on the aluminum            oxide layer are formed on an interface between the aluminum            oxide layer and the aluminum substrate;            -   ii) removing the aluminum oxide layer from the aluminum                substrate formed with the aluminum oxide layer thereon,                thereby forming a plurality of continuous half-spherical                recesses having a diameter of 25-1,000 mm on one surface                of the aluminum substrate; and            -   iii) forming a plurality of continuous half-spherical                convexes, having a diameter of 25-1,000 nm, on the first                main surface of a transparent substance by using the                aluminum substrate formed with a plurality of continuous                half-spherical recesses as a mold.

Another aspect of the present invention provides a method for preparingan organic light-emitting device, comprising the steps of:

-   -   a) adhering a transparent substance to a substrate;    -   b) before or after the a) step, forming a plurality of        continuous half-spherical convexes, having a diameter of        25-1,000 nm, on the first main surface of the transparent        substance by a method comprising the steps of;        -   i) dipping an aluminum substrate having at least one            aluminum surface in an acid solution, and applying an            oxidation voltage of 10-400 V to the aluminum substrate so            as to form an aluminum oxide layer on one surface of the            aluminum substrate, in such a manner that a plurality of            continuous recesses are formed on the aluminum oxide layer,            and a plurality of continuous recesses having a curvature in            identical direction to that of the recesses on the aluminum            oxide layer are formed on an interface between the aluminum            oxide layer and the aluminum substrate;        -   ii) removing the aluminum oxide layer from the aluminum            substrate formed with the aluminum oxide layer thereon,            thereby forming a plurality of continuous half-spherical            recesses having a diameter of 25-1,000 nm on one surface of            the aluminum substrate; and        -   iii) forming a plurality of continuous half-spherical            convexes, having a diameter of 25-1,000 nm, on the first            main surface of a transparent substance by using the            aluminum substrate formed with a plurality of continuous            half-spherical recesses as a mold;    -   c) preparing an organic light-emitting device by forming a first        electrode, an organic material layer(s) and a second electrode        on the upside of the substrate opposite to the side adhering the        transparent substance having continuous half-spherical convexes;        and optionally    -   d) adhering a transparent substance to the upside of the second        electrode that does not contact the organic material layer in        the organic light-emitting device; and    -   e) before or after the d) step, forming a plurality of        continuous half-spherical convexes, having a diameter of        25-1,000 nm, on the first main surface of the transparent        substance on the upside of the second electrode, by a method        comprising the steps of:        -   i) dipping an aluminum substrate having at least one            aluminum surface in an acid solution, and applying an            oxidation voltage of 10-400 V to the aluminum substrate so            as to form an aluminum oxide layer on one surface of the            aluminum substrate, in such a manner that a plurality of            continuous recesses are formed on the aluminum oxide layer,            and a plurality of continuous recesses having a curvature in            identical direction to that of the recesses on the aluminum            oxide layer are formed on an interface between the aluminum            oxide layer and the aluminum substrate;        -   ii) removing the aluminum oxide layer from the aluminum            substrate formed with the aluminum oxide layer thereon,            thereby forming a plurality of continuous half-spherical            recesses having a diameter of 25-1,000 nm on one surface of            the aluminum substrate; and        -   iii) forming a plurality of continuous half-spherical            convexes, having a diameter of 25-1,000 nm, on the first            main surface of a transparent substance by using the            aluminum substrate formed with a plurality of continuous            half-spherical recesses as a mold.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 shows an example of a conventional organic light-emitting device(101; glass substrate, 102: transparent anode, 103: hole injectionlayer, 104: hole transport layer, 105: light-emitting layer, 106;electron transport layer, 107: metal cathode).

FIG. 2 shows an example of an organic light-emitting device according tothe present invention (201: glass substrate, 202: transparent anode,203: hole injection layer, 204: hole transport layer, 205:light-emitting layer, 206: electron transport layer, 207: metal cathode,208: transparent substance having nano-sized convexes).

FIG. 3 shows a mold (301) formed with continuous nano-sizedhalf-spherical recesses and a transparent substance (302) formed withcontinuous nano-sized half-spherical convexes.

FIG. 4 shows a light route in an organic light-emitting device having aplanar transparent substrate and in an organic light-emitting devicehaving a transparent substrate adhering a transparent substance havingcontinuous nano-sized half-spherical convexes (401: organiclight-emitting device, 402: transparent substrate).

FIG. 5 shows a process for preparing an aluminum mold having continuousnano-sized half-spherical recesses (501: aluminum oxide layer, 502:aluminum substrate).

FIG. 6 is an electron micrograph showing the surface structure of asubstance having continuous nano-sized half-spherical convexes preparedin Example 1 ((a)×5,000, (b)×23,000).

FIG. 7 shows a schematic diagram of an organic light-emitting deviceaccording to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail, Theterm “nano-size” generally means the range of 1-1,000 nm in nanometerunit. However, in this specification, the term “nano-size” can beunderstood to mean 25-1,000 nm of the range of the diameter of therecesses or convexes that can be formed actually on an aluminumsubstrate or a transparent substance by the present invention.

In addition, the term “a first main surface of a transparent substance”in this specification means a surface formed with convexes by using analuminum substrate as a mold and opposite to a surface adhering device.

A transparent substance formed with continuous nano-sized convexes onits first main surface according to the present invention has a newstructure that can be prepared only by the method of the presentinvention as described below. The transparent substance can be used asan application for minimizing the condition of a total internalreflection in order to emit more light out of devices in a flat paneldisplay technical field. For example, when the transparent substanceaccording to the present invention is applied to an organiclight-emitting device, its principle is provided below.

In an organic light-emitting device comprising a substrate, a firstelectrode, an organic material layer(s) and a second electrode insequentially laminated form, the transparent substance formed withcontinuous nano-sized half-spherical convexes on its first main surfaceaccording to the present invention can be disposed on the underside ofthe substrate that does not contact the first electrode and/or theupside of the second electrode that does not contact the organicmaterial layer. Here, it should be noted that the half-sphericalconvexes according to the present invention are preferably disposed, noton the interior surface where the device is formed, but on the exteriorof the device, i.e., the underside of the substrate and/or the upside ofthe second electrode. Since an organic light-emitting device must beformed with a very thin thickness, in contrast to other light-emittingdevices such as an inorganic electroluminescent device, formation of anon-planar structure in the interior of the device can affect theoperation of the device.

As illustrated in FIG. 4, in an organic light-emitting device having asurface of a planar structure, the light generated may remain within theorganic light-emitting device by a total internal reflection. However,in an organic light-emitting device having continuous nano-sizedconvexes in its surface, the light may be emitted out of the device bymultiple reflections, preferably one or two times on the transparentsubstance. As shown in the principle above, an organic light-emittingdevice having a surface formed with continuous nano-sized convexesaccording to the present invention can emit more light out of thedevice.

In addition, since half-spherical convexes formed on the surface of anorganic light-emitting device according to the present invention arenano-sized and have a similar size to a wavelength of light, they canprovide far superior effects than a simple lens by an interaction withthe light emitted from the organic material layer. Accordingly,nano-sized half-spherical convexes of the present invention aredifferent from the micro-sized lens structure described in the prior art(WO 2003/7663). A further detailed explanation is provided below.

In the present invention, since half-spherical convexes on the substrateor electrode of the organic light-emitting device are nano-sized, thebrightness of the organic light-emitting device can be further improveddue to a wave character of light when light is emitted from the organicmaterial layer of the device. For instance, when a diameter of thehalf-spherical convexes is identical to or shorter than a wavelength ofa visible ray, the half-spherical convex structure may convert the routeof light by a diffused reflection or a scattering phenomenon of light.Therefore, the half-spherical convexes can cause more light to beemitted out of the organic light-emitting device by minimizing a totalinternal reflection condition more than the planar structure. Sucheffect may be increased when the diameter of the half-spherical convexesis set within a range between a half-wavelength and one wavelength ofthe visible ray.

In addition, according to the present invention, the transparentsubstance having a plurality of continuous half-spherical convexes onits first main surface is characterized by being prepared through aporous aluminum oxide layer forming process. The porous aluminum oxidelayer forming process is known in a technical field different from thisinvention's technical field. However, there are no cases of using theporous aluminum oxide layer forming process to prepare the transparentsubstance having nano-sized convexes. Inventors of the present inventionhave found that the transparent substance having nano-sized convexeswith a large size can be prepared at a low cost through the porousaluminum oxide layer forming process, and thus, the transparentsubstance having a non-planar structure can be applied to a flat paneldisplay device such as an organic light-emitting device with a largesize at a low cost.

In the present invention, in order to achieve the above effect of thepresent invention, half-spherical convexes disposed on the substrate orelectrode in the organic light-emitting device of the present inventionpreferably have a diameter of a range between a half wavelength and onewavelength of the visible ray, i.e., 200-800 nm. In addition, thehalf-spherical convexes are preferably uniformly distributed. In thepresent invention, the surface formed with continuous nano-sizedconvexes is illustrated in FIG. 7.

The porous aluminum oxide layer forming process has been disclosed in adocument entitled A. P. Li et al. J. Appl. Phys., 84, 6023 (1998), etc.A simple explanation is provided below. An aluminum substrate having atleast one aluminum surface is dipped in an appropriate acid solution,such as a sulfuric acid solution, a phosphoric acid solution, an oxalicacid solution or a chromic acid solution. Then, an appropriate oxidationvoltage, for example 10 to 400 V is applied to the aluminum substrate sothat an oxide layer, in which recesses having a diameter of about 25 to1,000 nm, preferably 200 to 800 nm, and a depth of about a few hundredsof nm to few μm are uniformly distributed, can be formed at the aluminumsubstrate. The depth of the recesses may increase proportionally to theprocessing time. At this time, at an interface between the oxide layerand the aluminum substrate, recesses having a curvature in identicaldirection to curvature of the half-spherical recesses on the oxide layerare formed.

FIG. 5 shows a forming process for an aluminum oxide layer through theabove method. In FIG. 5, steps a) to d) represent shape-variation of theoxide layer over time in the porous aluminum oxide layer formingprocess. At an initial stage, a thin and uniform oxide layer (501) isformed on an aluminum substrate (502) (see (a) in FIG. 5). After aperiod of time, as the volume of the oxide layer is expanded, a surfaceof the oxide layer is irregularly deformed (see, (b) in FIG. 5). Such anirregular surface of the oxide layer may cause an uneven currentdensity. That is, the current density may increase at a recess sectionof the oxide layer and may decrease at a protrusion section of the oxidelayer. Then, fine recesses are formed at the recess section having ahigh current density due to an operation of an electric field and anelectrolyte of the acid solution. The diameter of the fine recesses doesnot further increase after a predetermined time lapses (see, (c) in FIG.5). In addition, the depth of the recesses may rapidly increase in avertical direction with respect to the surface formed with the recesseswhile constantly maintaining the number of the recesses (see (d) in FIG.5). As the depth of the recesses increases, recesses having a curvaturein identical direction to the curvature of the recesses on the aluminumoxide layer are formed at an interface of the aluminum oxide layer (501)and the aluminum substrate (502) (see (c) and (d) in FIG. 5).

After forming a porous oxide layer on the aluminum substrate by theprocess explained above, a substrate formed with a plurality ofcontinuous half-spherical recesses as (e) in FIG. 5 can be prepared byremoving the porous oxide layer from the aluminum substrate. The oxidelayer can be removed through a chemical etching process, anelectrochemical etching process or an electrical shock process, etc.However, the present invention does not limit the process for removingthe oxide layer.

According to the chemical etching process, the oxide layer is etched byusing an acid solution. The example of the acid solution includes amixture of a phosphoric acid solution and a chromic acid solution.According to the electrochemical etching process, a substrate formedwith the oxide layer is used as an electrode and the substrate is dippedin the acid solution so that the oxide layer is removed from thesubstrate through an electrochemical reaction. The example of the acidsolution includes a mixture of ethanol and HClO₄. According to theelectrical shock process, electric shock is applied to the substrate byelectrochemically adjusting the voltage, thereby removing the oxidelayer from the aluminum substrate.

In the process, if the aluminum substrate includes at least one aluminumsurface, the remaining material of the aluminum substrate is not limitedto specific materials. For instance, a substrate consisting of aluminumcan be used in the present invention, and a substrate consisting of analuminum layer laminated on another substrate such as a glass substratealso can be used.

Then, nano-sized half-spherical convexes, which are inverted structuresof nano-sized half-spherical recesses, can be formed on the transparentsubstance by using the aluminum substrate formed with continuousnano-sized half-spherical recesses as a mold. For this purpose, themethods known for this technical field may be used and the presentinvention is not limited to specific methods.

The material for the transparent substance preferably includes somethingable to be used as a replica molding material that can remain andflatten the shape of nano-sized half-spherical recesses in the aluminumsubstrate. Most polymers can be used as the material for the transparentsubstance. However, the transparent substance having nano-sizedhalf-spherical convexes for being applied to an organic light-emittingdevice of the present invention needs to have good transmission at thevisible range of light. Therefore, the material for the transparentsubstance more preferably is a polymer that has no less than 60% oftransmittance for a visible ray after being formed nano-sizedhalf-spherical convexes thereon. The material satisfying said conditionincludes PDMS (poly(dimethylsiloxane) [see, T. M. Odom et al. Langmuir,18, 5314 (2002)] or PMMA (polymethylmethacrylate) [see, H. Tan et al. J.vac. Sci. Technol. B, 16, 3926 (1998)], but is not limited to them.

One method for forming continuous nano-sized half-spherical convexes onthe transparent substance consisting of such material may be anano-imprint technique.

A nano-imprint technique is a method that uses a substrate having anano-sized structure as a mold for preparing a film having an invertedmold structure. That is, a film is formed on a substrate having anano-sized structure by using a material that can remain and flatten thestructure of the substrate, such as PDMS or PMMA. Such film can beformed by a method such as pouring or spin-coating such material inmolten state on the mold substrate, etc. If bubbles are generated on thefilm, the bubbles can be removed by curing the film under a vacuum.Then, a film having an inverted structure of a nano-sized structure onthe mold can be prepared by curing the film through heat or ultravioletand then taking off the substrate used as the mold.

In the method, it is preferable that the bonding between the mold andtransparent film having an inverted structure of the mold's structure isweakened, for transferring the nanometer-sized structure. In thisregard, the mold substrate may be dipped in a solution comprising amaterial able to reduce a surface energy of the mold substrate, orformed with a release layer thereon by exposing the mold substrate tothe vapor of a material able to reduce a surface energy of the moldsubstrate, and then washing the mold substrate. The material able toreduce the surface energy of the mold substrate includestridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane, etc. However, thepresent invention is not limited to such methods and may use methodsknown in the art in order to achieve the same effect as the one achievedby the release layer.

In the nano-imprint technique, said aluminum substrate having continuousnano-sized half-spherical recesses can be used as the mold substrate,but a polymer mold having continuous nano-sized half-spherical recessesprepared by repeating the nano-imprint technique more than 2 times byusing the aluminum substrate as a mold also can be used. At this time,the material for the polymer mold includes hard polymer materials, forexample, polyurethane, etc. In order to complement the hardness of thepolymer mold and facilitate separation between the polymer mold and thetransparent substance in the preparation of the transparent substancehaving continuous nano-sized half-spherical convexes, a scratchresistant thin layer consisting of polystyrene or polycarbonate, etc. ormetal thin layer may be formed on the polymer mold. The aluminum orpolymer mold can be used more than 10 times through a simple washing.

Another method for forming continuous nano-sized half-spherical convexeson the transparent substance may be a method that forms continuousnano-sized half-spherical convexes by appropriately pressing thetransparent substance by the aluminum mold having continuous nano-sizedhalf-spherical recesses while curing the transparent substance byultraviolet or heat. In such method, the continuous nano-sizedhalf-spherical convexes can be formed on the transparent substance byadhering the mold to a roller or forming continuous nano-sizedhalf-spherical recesses on a roller, and then performing a roll processby such roller [see, H. Tan et al. J. Vac. Sci. Technol. B, 16, 3926(1998)].

In the present invention, the transparent substance prepared asdescribed above can be applied to devices that need to minimize thecondition of a total internal reflection. Recently, such relief of atotal internal reflection is required in a flat panel display devicefield, but the application of the transparent substance of thisinvention is not limited to it. In one embodiment of the presentinvention, the transparent substance according to the present inventioncan be applied to an organic light-emitting device.

An organic light-emitting device having continuous nano-sizedhalf-spherical convexes can be prepared by adhering the transparentsubstance of the present invention to a transparent substrate and/or atransparent electrode, and forming continuous nano-sized half-sphericalconvexes on the transparent substance by the method as described abovebefore or after adhering the transparent substance to the substrate orthe electrode. The process that adheres the transparent substance to thetransparent substrate or transparent electrode and the process thatforms continuous nano-sized half-spherical convexes on the transparentsubstance may be performed before or after preparing the organiclight-emitting device.

In the present invention, the method adhering the transparent substanceto the substrate or electrode is not limited to a specific method, andthe present invention may use methods known in the art.

One example of the method adhering the transparent substance to thesubstrate or electrode of the device is a method comprising the steps ofactivating the surface of the substrate or electrode by oxygen plasma,etc., and then adhering the transparent substance to the substrate orelectrode by heat or ultraviolet so as to remove an air layer betweenthe transparent substance and the substrate or electrode.

Another example of the method adhering the transparent substance to thesubstrate or electrode of the device is a method that forms aself-assembled monolayer (SAM) on the substrate or electrode to improveadhesion between the transparent substance and the substrate orelectrode. As an example, in order to improve adhesion between a glasssubstrate and a PDMS substance, the SAM can be formed on the glasssubstrate by dissolving 5-hexenyltrichlorosilane in a solvent such astoluene, and then dipping the glass substrate in the solution.

Another method adhering the transparent substance to the substrate orelectrode is a method that forms a polymer film by a method comprisingthe step of pouring or spin-coating the material of the transparentsubstance in the molten state on the substrate or electrode.

In the present invention, when the transparent substance is adhered to atransparent substrate, a material having mechanical and thermalstability and low permeability for water and oxygen preferably may beused as a material for the transparent substrate. Preferable examples ofthe material include glass, quartz, polymers, and materials having alaminated structure of metal oxides having a good barrier property forwater and oxygen. However, the present invention is not limited to them.

The organic light-emitting device of the present invention can beprepared by methods known in the art and can have a structure known inthe art, except for having continuous nano-sized half-spherical convexeson the surface of the substrate and/or electrode of the device by themethod as described above.

According to one embodiment of the present invention, the organiclight-emitting device may have a structure as shown in FIG. 2. Theorganic light-emitting device shown in FIG. 2, can be prepared bydepositing an anode (202) on the transparent substrate (201) adheringthe transparent substance (208) having continuous nano-sizedhalf-spherical convexes, using a metal, a metal oxide havingconductivity, or an alloy thereof, then forming organic material layerscomprising a hole injection layer (203), a hole transport layer (204), alight-emitting layer (205) and a electron transport layer (206), etc.thereon, and then depositing a material used for a cathode (207)thereon, by a physical vapor deposition (PVD) such as an E-beamevaporation or a sputtering, etc.

In addition to such method, an organic light-emitting device can beprepared by sequentially depositing a cathode material, an organicmaterial layer, and an anode material on the substrate (see, WO2003/012890). The organic material layer may have the form of a singlelayer structure or a multi-layer structure comprising a hole injectionlayer, a hole transport layer, a light-emitting layer and an electrontransport layer, etc. The organic material layer may be formed in asmaller number of layers through a solvent process, such as a spincoating process, a screen-printing process or an ink jet process usingvarious polymer materials, instead of a physical vapor depositionprocess.

The anode preferably may be prepared by using a material having a highwork function in order to allow holes to be easily injected into theorganic material layer. Particularly, the material for the anodeincludes metals, such as vanadium, chrome, copper, zinc, gold, or analloy thereof; metal oxides, such as a zinc oxide, an indium oxide, anindium tin oxide (ITO), or an indium zinc oxide (IZO); a mixture of ametal and an oxide, such as ZnO:Al or SnO₂:Sb; and conductive polymers,such as poly (3-methylthiophene), poly [3,4-(ethylene-1,2-dioxy)thiophene (PEDT), polypyrrole, and polyaniline, etc. However, thepresent invention does not limit the material for the anode. In order toemit the light through the anode in the organic light-emitting device, amaterial having a high transparent degree (>50%), particularly a metaloxide such as zinc oxide, indium oxide, indium tin oxide (ITO) andindium zinc oxide (IZO), or a thin metal layer, etc preferably may beused as the material for the anode. In addition, in order to emit thelight through the cathode in the organic light-emitting device, amaterial having a high reflectance (>50%) preferably may be used as thematerial for the anode, and more preferably Ag, Al, Ni, Cr, Au or analloy thereof, etc. may be used.

The cathode preferably may be prepared by using a material having a lowwork function in order to allow electrons to be easily injected into theorganic material layer. Specifically, the material for the cathodeincludes metals, such as Mg, Ca, Na, K, Ti, In, Yt, Li, Gd, Al, Ag, Sn,Pb, or an alloy of the same; and multi-layer materials such as LiF/Al orLiO₂/Al, However, the present invention does not limit the material forthe cathode. In order to emit the light through the cathode in theorganic light-emitting device, a material having a high transparentdegree (>50%) preferably may be used as the material for the cathode.Particularly, a material prepared by depositing a transparent conductivematerial such as indium tin oxide or indium zinc oxide on a transparentthin layer consisting of Al or a mixture of Mg and Ag is more preferred.

The hole injection layer is prepared by using a material capable ofallowing holes to be injected from the anode at a low voltage condition.It is preferred that the material for the hole injection layer has anHOMO (highest occupied molecular orbital) between the work function ofthe anode material and the HOMO of a peripheral organic material layer.Specifically, the material for the hole injection layer includes metalporphyrine, oligothiophene, arylamine-based organic materials,hexanitrile hexaazatriphenylene, quinacridone-based organic materials,perylene-based organic materials, anthraquinone-based conductivepolymer, polyaniline and polythiophene-based conductive polymer orconductive polymer such as a dopant. However, the present invention doesnot limit the material for the hole injection layer.

The hole transport layer is prepared by using a material capable oftransporting holes from the anode or the hole injection layer to thelight-emitting layer. It is preferred that the material for the holetransport layer has a high hole mobility. Specifically, the material forthe hole transport layer includes arylamine-based organic materials,conductive polymers, and block copolymers including a conjugate sectionand a non-conjugate section, etc. However, the present invention doesnot limit the material for the hole transport layer.

The light-emitting layer is prepared by using a material capable ofgenerating light of a visible ray range by combining holes withelectrons transferred from the hole transport layer and the electrontransport layer, respectively. It is preferred that the material for thelight-emitting layer represents a superior quantum efficiency withrespect to fluorescence or phosphorescence. Specifically, the materialfor the light-emitting layer includes 8-hydroxy-quinoline aluminumcomplex (Alq₃), carbazole-based compounds, dimerized styryl compounds,BAlq, 10-hydroxybenzo quinoline-metal compounds, compounds based onbenzoxazole, benzthiazole, and benzimidazole,poly(p-phenylenevinylene)-based polymers, poly phenylenevinylene(PPV)-based polymers, spiro compounds, polyfluorene, rubrene,etc. However, the present invention does not limit the material for thelight-emitting layer.

The electron transport layer is prepared by using a material capable oftransporting electrons from the cathode to the light-emitting layer. Itis preferred that the material for the electron transport layer has ahigh electron mobility. Specifically, the material for the electrontransport layer includes 8-hydroxy-quinoline aluminum complex, complexesincluding Alq₃, organic radical compounds, and hydroxyflavone-metalcomplexes, etc. However, the present invention does not limit thematerial for the electron transport layer.

The organic light-emitting device according to the present invention maybe a top emission type, a bottom emission type or a bilateral emissiontype, depending on used materials.

EXAMPLES Example 1 Preparation of an Organic Light-Emitting Device

Glass substrate (corning 7059 glass) coated with a thin layer of ITO(indium tin oxide) having a thickness of 1,000 Å was washedultrasonically in distilled water in which a detergent was dissolved. Inthe process, a detergent made from Fischer Co. and distilled waterprepared by filtering water 2 times using a filter made from MilliporeCo. were used. After ITO was washed for 30 minutes as mentioned above,it was subjected to ultrasonic washing 2 times for 10 minutes. Afterthen, it was washed by isopropyl alcohol, acetone, and methanol solventsequentially by ultrasonic wave, and then dried.

Hexanitrile hexaazatriphenylene (500 Å),4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) (400 Å)), Alq₃ (300Å) and a compound represented as the following formula 1 weresequentially deposited on the ITO electrode by a thermal vacuumdeposition, thereby forming a hole injection layer, a hole transportlayer, a light-emitting layer and an electron transport layer,sequentially.

Then, lithium fluoride (LiF) having a thickness of 12 Å and aluminumhaving a thickness of 2000 Å were sequentially deposited on the electrontransport layer so as to form a cathode, thereby forming an organiclight-emitting device.

In the above process, the deposition rate of the organic materials wasmaintained at 0.4 to 0.7 Å/sec, the deposition rate of the LiF of thecathode was maintained at 0.3 Å/sec, the deposition rate of aluminum wasmaintained at 2 Å/sec, and the vacuum level was maintained at 2×10⁻⁷ to5×10⁻⁸ torr during the deposition process.

Preparation of Aluminum Mold Having Continuous Nano-Sized Half-SphericalRecesses

After dipping the aluminum substrate in a phosphoric acid solution, anoxidation voltage of 196 V was applied to the aluminum substrate,thereby forming an aluminum oxide layer formed with uniform recesseshaving a diameter of about 200-600 nm and a thickness of about a few tanon the aluminum substrate. Then, the aluminum oxide layer was removedfrom the aluminum substrate by performing a chemical etching processusing a mixture of the phosphoric acid solution and a chromic acidsolution, thereby obtaining an aluminum substrate having continuousnano-sized half-spherical recesses.

The aluminum substrate was subjected to an oxygen plasma treatment andthen exposed to vapor oftridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane. Then, the aluminumsubstrate was washed using toluene so as to obtain a release layerconsisting of tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilanemonolayer on the aluminum substrate.

Preparation of a Transparent Substance Having Continuous Nano-SizedHalf-Spherical Convexes and Application Thereof to the OrganicLight-Emitting Device

A mixture of a PDMS and a curing agent (Sylgard 184, Dow-Corning) in theratio of 10:1 was poured on the aluminum substrate prepared as describedabove, and then the aluminum substrate was rotated at 3000 rpm so as toform a PDMS layer on the aluminum substrate. Then, the aluminumsubstrate was removed and the PDMS layer was obtained.

The underside of the glass substrate that did not contact the ITOelectrode in the organic light-emitting device prepared as describedabove, was subjected to an oxygen plasma treatment for activation ofglass surface. Then, the organic light-emitting device being treated asabove was dipped in a toluene solution, in which 5-hexenyltrichlorosilane was dissolved, for 30 minutes so as to form aself-assembled monolayer consisting of 5-hexenyl trichlorosilane on theglass substrate.

The surface of the glass substrate being treated with 5-hexenyltrichlorosilane in the organic light-emitting device was contacted withthe PDMS layer. After curing the organic light-emitting device at 65° C.under vacuum, the organic light-emitting device having continuousnano-sized half-spherical convexes was obtained. FIG. 6 shows thestructure of continuous nano-sized half-spherical convexes formed on theorganic light-emitting device.

Results of Light-Emitting Experiments

When a forward electric field of 6 V was applied to the organiclight-emitting device prepared as above, green emission corresponding to3200 nit was observed from Alq₃.

Comparative Example 1

The organic light-emitting device was prepared using the same process asExample 1, except for not adhering the PDMS film having continuousnano-sized half-spherical on the transparent substrate of the organiclight-emitting device.

When a forward electric field of 6 V was applied to the organiclight-emitting device formed on the planar glass substrate having nonano-sized half-spherical convexes, green emission corresponding to 2300nit was observed from Alq₃.

Comparative Example 2

The organic light-emitting device was prepared using the same process asExample 1, except for adhering a PDMS film having a planar structure onthe transparent substrate of the organic light-emitting device.

When a forward electric field of 6 V was applied to the organiclight-emitting device formed on the planar glass substrate having nonano-sized half-spherical convexes, green emission corresponding to 2100nit was observed from Alq₃.

Through the results of Example 1 and Comparative Examples 1 and 2, itcan be understood that the organic light-emitting device havingcontinuous nano-sized convexes emit more light than the device having aplanar surface, even if both of them were prepared by using identicalorganic materials.

INDUSTRIAL APPLICABILITY

The transparent substance having continuous nano-sized half-sphericalconvexes according to the present invention can be used for minimizingthe condition of a total internal reflection in a technical field of aflat panel display such as an organic light-emitting device, etc. Anorganic light-emitting device having non-planar structure by beingapplied with the transparent substance having continuous nano-sizedhalf-spherical convexes according to the present invention, canmaximally emit light generated from the organic material layer out ofthe organic light-emitting device, compared with an organiclight-emitting device of a planar structure. In addition, sincecontinuous nano-sized half-spherical convexes according to the presentinvention can be prepared by using the aluminum substrate havingcontinuous nano-sized half-spherical recesses prepared by a porousaluminum oxide layer forming process, as a mold, it can economically beapplied to a large area. Therefore, the organic light-emitting device ofthe present invention can also be economically used in a large-sizedapplication.

1. A transparent substance wherein a plurality of continuoushalf-spherical convexes having a diameter of 25-1,000 nm are formed on afirst main surface of the transparent substance.
 2. The transparentsubstance according to claim 1, prepared by a method comprising thesteps of: a) dipping an aluminum substrate having at least one aluminumsurface in an acid solution, and applying an oxidation voltage of 10-400V to the aluminum substrate so as to form an aluminum oxide layer on onesurface of the aluminum substrate, in such a manner that a plurality ofcontinuous recesses are formed on the aluminum oxide layer, and aplurality of continuous recesses having a curvature in identicaldirection to that of the recesses on the aluminum oxide layer are formedon an interface between the aluminum oxide layer and the aluminumsubstrate; b) removing the aluminum oxide layer from the aluminumsubstrate formed with the aluminum oxide layer thereon, thereby forminga plurality of continuous half-spherical recesses having a diameter of25-1,000 nm on one surface of the aluminum substrate; and c) forming aplurality of continuous half-spherical convexes, having a diameter of25-1,000 nm, on the first main surface of a transparent substance byusing the aluminum substrate formed with a plurality of continuoushalf-spherical recesses as a mold.
 3. The transparent substanceaccording to claim 1, wherein the transparent substance consists of apolymer material having no less than 60% of transmittance in the rangeof visible ray.
 4. The transparent substance according to claim 1,wherein the transparent substance consists of at least one materialselected from a group consisting of poly(dimethylsiloxane) (PDMS) andpolymethylmethacrylate (PMMA).
 5. The transparent substance according toclaim 1, applied to a device that requires the minimization of a totalinternal reflection condition.
 6. The transparent substance according toclaim 5, wherein the device is an organic light-emitting device.
 7. Anorganic light-emitting device comprising a substrate, a first electrode,an organic material layer(s) and a second electrode in the sequentiallylaminated form, wherein a plurality of continuous half-sphericalconvexes having a diameter of 25-1,000 nm are formed on the underside ofthe substrate that does not contact the first electrode, the upside ofthe second electrode that does not contact the organic material layer,or both of them.
 8. The organic light-emitting device according to claim7, wherein the organic material layer comprises a hole injection layer,a hole transport layer, a light-emitting layer and an electron transportlayer.
 9. The organic light-emitting device according to claim 7,prepared by a method comprising the steps of: a) preparing an organiclight-emitting device by forming a first electrode, an organic materiallayer(s) and a second electrode on a substrate; b) adhering atransparent substance to the underside of the substrate that does notcontact the first electrode, the upside of the second electrode thatdoes not contact the organic material layer, or both of them in theorganic light-emitting device; c) before or after the b) step, forming aplurality of continuous half-spherical convexes, having a diameter of25-1,000 nm, on a first main surface of the transparent substance by amethod comprising the steps of: (i) dipping an aluminum substrate havingat least one aluminum surface in an acid solution, and applying anoxidation voltage of 10-400 V to the aluminum substrate so as to form analuminum oxide layer on one surface of the aluminum substrate, in such amanner that a plurality of continuous recesses are formed on thealuminum oxide layer, and a plurality of continuous recesses having acurvature in identical direction to that of the recesses on the aluminumoxide layer are formed on an interface between the aluminum oxide layerand the aluminum substrate; (ii) removing the aluminum oxide layer fromthe aluminum substrate formed with the aluminum oxide layer thereon,thereby forming a plurality of continuous half-spherical recesses havinga diameter of 25-1,000 nm on one surface of the aluminum substrate; and(iii) forming a plurality of continuous half-spherical convexes, havinga diameter of 25-1,000 nm, on the first main surface of a transparentsubstance by using the aluminum substrate formed with a plurality ofcontinuous half-spherical recesses as a mold.
 10. The organiclight-emitting device according to claim 7, prepared by a methodcomprising the steps of: a) adhering a transparent substance to asubstrate; b) before or after the a) step, forming a plurality ofcontinuous half-spherical convexes, having a diameter of 25-1,000 nm, ona first main surface of the transparent substance by a method comprisingthe steps of: (i) dipping an aluminum substrate having at least onealuminum surface in an acid solution, and applying an oxidation voltageof 10-400 V to the aluminum substrate so as to form an aluminum oxidelayer on one surface of the aluminum substrate, in such a manner that aplurality of continuous recesses are formed on the aluminum oxide layer,and a plurality of continuous recesses having a curvature in identicaldirection to that of the recesses on the aluminum oxide layer are formedon an interface between the aluminum oxide layer and the aluminumsubstrate; (ii) removing the aluminum oxide layer from the aluminumsubstrate formed with the aluminum oxide layer thereon, thereby forminga plurality of continuous half-spherical recesses having a diameter of25-1,000 nm on one surface of the aluminum substrate; and (iii) forminga plurality of continuous half-spherical convexes, having a diameter of25-1,000 nm, on the first main surface of a transparent substance byusing the aluminum substrate formed with a plurality of continuoushalf-spherical recesses as a mold; c) preparing an organiclight-emitting device by forming a first electrode, an organic materiallayer(s) and a second electrode on the upside of the substrate oppositeto the side adhering the transparent substance having continuoushalf-spherical convexes.
 11. The organic light-emitting device accordingto claim 9, wherein the transparent substance consists of a polymermaterial having no less than 60% of permeability for a visible ray. 12.The organic light-emitting device according to claim 11, wherein thetransparent substance consists of at least one material selected from agroup consisting of poly(dimethylsiloxane) (PDMS) andpolymethylmethacrylate (PMMA).
 13. A method for preparing a transparentsubstance, wherein a plurality of continuous half-spherical convexeshaving a diameter of 25-1,000 nm are formed on a first main surface ofthe transparent substance, comprising the steps of: a) dipping analuminum substrate having at least one aluminum surface in an acidsolution, and applying an oxidation voltage of 10-400 V to the aluminumsubstrate so as to form an aluminum oxide layer on one surface of thealuminum substrate, in such a manner that a plurality of continuousrecesses are formed on the aluminum oxide layer, and a plurality ofcontinuous recesses having a curvature in identical direction to that ofthe recesses on the aluminum oxide layer are formed on an interfacebetween the aluminum oxide layer and the aluminum substrate; b) removingthe aluminum oxide layer from the aluminum substrate formed with thealuminum oxide layer thereon, thereby forming a plurality of continuoushalf-spherical recesses having a diameter of 25-1,000 nm on one surfaceof the aluminum substrate; and c) forming a plurality of continuoushalf-spherical convexes, having a diameter of 25-1,000 nm, on the firstmain surface of a transparent substance by using the aluminum substrateformed with a plurality of continuous half-spherical recesses as a mold.14. A method for preparing an organic light-emitting device, comprisingthe steps of: a) preparing an organic light-emitting device by forming afirst electrode, an organic material layer(s) and a second electrode ona substrate; b) adhering a transparent substance to the underside of thesubstrate that does not contact the first electrode, the upside of thesecond electrode that does not contact the organic material layer, orboth of them in the organic light-emitting device; c) before or afterthe b) step, forming a plurality of continuous half-spherical convexes,having a diameter of 25-1,000 nm, on a first main surface of thetransparent substance by a method comprising the steps of: (i) dippingan aluminum substrate having at least one aluminum surface in an acidsolution, and applying an oxidation voltage of 10-400 V to the aluminumsubstrate so as to form an aluminum oxide layer on one surface of thealuminum substrate, in such a manner that a plurality of continuousrecesses are formed on the aluminum oxide layer, and a plurality ofcontinuous recesses having a curvature in identical direction to that ofthe recesses on the aluminum oxide layer are formed on an interfacebetween the aluminum oxide layer and the aluminum substrate; (ii)removing the aluminum oxide layer from the aluminum substrate formedwith the aluminum oxide layer thereon, thereby forming a plurality ofcontinuous half-spherical recesses having a diameter of 25-1,000 nm onone surface of the aluminum substrate; and (iii) forming a plurality ofcontinuous half-spherical convexes, having a diameter of 25-1,000 nm, onthe first main surface of a transparent substance by using the aluminumsubstrate formed with a plurality of continuous half-spherical recessesas a mold.
 15. A method for preparing an organic light-emitting device,comprising the steps of: a) adhering a transparent substance to asubstrate; b) before or after the a) step, forming a plurality ofcontinuous half-spherical convexes, having a diameter of 25-1,000 nm, ona first main surface of the transparent substance by a method comprisingthe steps of: (i) dipping an aluminum substrate having at least onealuminum surface in an acid solution, and applying an oxidation voltageof 10-400 V to the aluminum substrate so as to form an aluminum oxidelayer on one surface of the aluminum substrate, in such a manner that aplurality of continuous recesses are formed on the aluminum oxide layer,and a plurality of continuous recesses having a curvature in identicaldirection to that of the recesses on the aluminum oxide layer are formedon an interface between the aluminum oxide layer and the aluminumsubstrate; (ii) removing the aluminum oxide layer from the aluminumsubstrate formed with the aluminum oxide layer thereon, thereby forminga plurality of continuous half-spherical recesses having a diameter of25-1,000 nm on one surface of the aluminum substrate; and (iii) forminga plurality of continuous half-spherical convexes, having a diameter of25-1,000 nm, on the first main surface of a transparent substance byusing the aluminum substrate formed with a plurality of continuoushalf-spherical recesses as a mold; c) preparing an organiclight-emitting device by forming a first electrode, an organic materiallayer(s) and a second electrode on the upside of the substrate oppositeto the side adhering the transparent substance having continuoushalf-spherical con-vexes.
 16. The method for preparing an organiclight-emitting device according to claim 15, further comprising: d)adhering a transparent substance to the upside of the second electrodethat does not contact the organic material layer in the organiclight-emitting device; and e) before or after the d) step, forming aplurality of continuous half-spherical convexes, having a diameter of25-1,000 nm, on the first main surface of the transparent substance onthe upside of the second electrode, by a method comprising the steps of:(i) dipping an aluminum substrate having at least one aluminum surfacein an acid solution, and applying an oxidation voltage of 10-400 V tothe aluminum substrate so as to form an aluminum oxide layer on onesurface of the aluminum substrate, in such a manner that a plurality ofcontinuous recesses are formed on the aluminum oxide layer, and aplurality of continuous recesses having a curvature in identicaldirection to that of the recesses on the aluminum oxide layer are formedon an interface between the aluminum oxide layer and the aluminumsubstrate; (ii) removing the aluminum oxide layer from the aluminumsubstrate formed with the aluminum oxide layer thereon, thereby forminga plurality of continuous half-spherical recesses having a diameter of25-1,000 nm, on one surface of the aluminum substrate; and (iii) forminga plurality of continuous half-spherical convexes, having a diameter of25-1,000 nm, on the first main surface of a transparent substance byusing the aluminum substrate formed with a plurality of continuoushalf-spherical recesses as a mold.
 17. The organic light-emitting deviceaccording to claim 10, wherein the transparent substance consists of apolymer material having no less than 60% of transmittance in the rangeof a visible ray.
 18. The organic light-emitting device according toclaim 17, wherein the transparent substance consists of at least onematerial selected from a group consisting of poly(dimethylsiloxane)(PDMS) and polymethylmethacrylate (PMMA).